Roll forming machinery usually has a plurality of sets of rolls, usually arranged in upper and lower pairs, and usually spaced apart along the length of the machine on roller stands. Typically, the roller dies at one stand will produce a continuous formation in the web, and the roller dies of the next stand will produce another formation, or for example increase the angle of the formation which has already been started at the previous stand and so on.
A wide variety of commercial and other products are made on such-roll forming machines, such as roof decking siding, and a large number of components for consumer equipment. The shapes may simply be webs with edge formations formed along one edge or both, or may be C sections or U sections but in many cases consist of relatively complex formations with longitudinal formations being formed along the length of the web, side by side.
Generally speaking at each stand of rolls there are two lower dies and two upper dies arranged in pairs, to form the web on either side of a central web axis. The lower dies engage the underside of the web and the upper dies engage the upper side of the web. The dies have circular shapes, and are mounted on rotatable axles so that the dies can rotate at the same speed as the sheet metal.
A gear drive mechanism is coupled to the dies so as to drive them at the speed of the sheet metal.
Each set of such roller dies must be designed to provide a particular formation in the web. In addition, each pair of dies must have a clearance between them determined by the thickness of the web.
Thus where it is desired to discontinue working on a web of one thickness, and to then run a web of another thickness through the dies, each pair of roller dies must be readjusted to a new clearance, to accommodate the new thickness of the new web. This involves costly down time, in order to make the fine adjustments.
All of this is very well known in the art and is accepted as the normal operating procedure.
It is however well known that a further problem exists in roll forming. The web of sheet material which provides the basic feed stock for the roller machine should preferably maintain its thickness within very narrow limits, along the entire length of the web. If there is any significant variation in thickness in the web, then the dies, being fixed as to clearance, will produce varying effects on the web as the web passes along the roller stands, or the web may jam causing stoppage of the line.
In practice, it is well known that some web material varies in thickness to a greater extent than is permissible. This results in unusual effects being produced in the final formed web, which may warp or bend or twist, or even jam.
Generally speaking, it is not possible to adjust the clearances of the roller dies, during the actual operation of the machine, and the best that can be done is that in the initial set up, the machinist will set the die clearances to a predetermined average web thickness. The results obtained in this way however are not always entirely satisfactory.
It would in theory be desirable to provide for automatic self-adjustment of the spacings or clearances between the pairs of dies in each stand. However, due to the shaping of the dies there are difficulties in such adjustments. Usually the dies will have two surfaces, one of the surfaces being more or less horizontal, or at least parallel to the plane of the web itself and the other of the surfaces being at a web forming angle.
Another set of problems arises if it is desired to use the same roller dies, to form a web having a width which is greater, or narrower than a preceding web.
In the past each of the stands would have to be manually moved further apart, or closer together, to take in to account the width of the new web to be processed. However, it was time consuming to dismantle the arrangement of dies for one web width, and then reassemble the dies with a greater or lesser number of rolls between them to suit the new web width. In addition, this was awkward and time consuming manual work.
It is therefore desirable to provide for roller die stands arranged in pairs, in which one of each of the stands in each of the pairs shall be transversely moveable relative to the other.
Given both die clearance adjustment, and stand width adjustment, it would be possible, using one set of roller die stands and dies, to provide for the processing of webs both of different thicknesses, and also of different widths. This enables a manufacturer to produce a standard rolled form section such as a "C" section in a variety of widths and in a variety of gauges, from a single machine. This would reduce the capital investment in machinery. In addition would reduce the down time required for change over from one web to another and also reduce the need for skilled labour.
Additional savings would be achieved if the spacer rolls could be introduced between the paris of dies by some form of powered mechanism.
A further problem arises with roll forming certain sections, particularly sections which have the shape of a letter C with inturned flanges, or a partially closed-in box section.
In this type of section, the two edges or flanges of the C, or partially closed-in box, are turned inwardly. This is usually done by roll forming the edge flanges first, and then roll forming the C bends later, i.e. downstream. Special dies are required to form the last bends, and it is desirable to provide for adjustment of these dies. Adjustment of such dies in this location however, to accommodate variations in web thickness and to form different sizes of C-section presents further problems.